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Evolution
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Evolution – any process of change over time.
Geologic Time – A record of Earth’s history found in rocks and fossils. Earth’s age – about 4.6 billion yrs. Relative age of rocks determined by their position.
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Grand Canyon Older fossils show that life forms started as simple, single celled organisms.
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History of Evolution 1. Lamarck (1809) – thought evolution resulted from striving for improvement. - a) organs appeared as needed and could be improved with use. Then passed to offspring.
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-b) If not needed, organs disappeared in next generation.
-c) Transmission of acquired traits. (lose an arm, offspring could be born that way) Weismann(1870) – disproved Lamarck. Cut off tails of mice and all the offspring still had tails.
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Charles Darwin
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The Voyage of the Beagle
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Darwin’s Theory of Natural Selection based on:
1. Overproduction – due to limited space and food, more offspring produced than can survive. 2. Competition - members of a population compete for food and mates.
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3. Variation – because of different characteristics, some better able to survive.
4. Survival of the fittest – those that survive longer will live to reproduce. 5. Transmission of favorable traits – offspring of fittest parents will inherit their favorable traits.
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6. Evolution – as populations change due to these new favorable traits, that is evolution
ameoba sisters natural selection
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Modern Theory of Evolution
Variation – caused by “shuffling” of genes during sexual reproduction. Also caused by random mutations Natural Selection – due to passing on of genes for favorable traits. Geographic Isolation – 1 species can become 2 different ones if a population gets separated by mountains or plates separating.
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Environmental Changes – stable environment = not much change
- changes in the environment select for different traits to become successful. ex: antibiotics lead to resistant strains of bacteria
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Rates of Evolutionary Change
1. Gradualism – changes occur little by little over long time. 2. Punctuated Equilibrium – things are stable until brief, fast change occurs. Then stable again.
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Similarities between related species
** Species with short life spans and large numbers of offspring can change very quickly. Ex: bacteria, insects Similarities between related species Comparative Anatomy – similar body structures
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Homologous Structures – same structure different function
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Analagous structures – similar function but different structure
Analagous structures – similar function but different structure. Not close relationship
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Similar cell parts
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Similar embryos
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